1. Field of the Invention
This invention relates to fittings used in the ducting of central heating and air conditioning systems, and more particularly, to an air duct boot utilized to terminate ducting in an air register located at the air discharge location.
2. Description of the Prior Art
In the construction of buildings which are to be provided with central heating and air conditioning, a network of ducts is extended from a central source of heat or cool air into the various rooms for discharging the heated or cooled air into the rooms. At the ground level, these ducts are frequently laid horizontally with or beneath a slab or pad from the central location where the cooling or heating of the air is developed. The ducts then terminate in short, vertically extending legs which end at the surface of the floor within the particular room where the air is to be discharged. In reaching this location, the short, vertical leg of the duct, which may be referred to as a boot, ends at its upper terminus at approximately floor level in an opening surrounded by a round or rectangular portion of the material of which the duct is constructed. At this location, an air register or grate is fitted over or into the upper end of the boot to prevent various objects from falling into the boot and air duct.
One type of air duct boot which has been utilized as a metallic (usually sheet metal) housing having an open lower end and an open upper end, with the lower end being disposed in the sand upon which the pad or slab for the building is laid.
U. S. Pat. No. 4,623,170 to Cornwall, discloses a synthetic resin coupling sleeve which can be positioned in a concrete slab or other foundation structure, and which facilitates the securement of a pipe into and through the concrete. The coupling is of cylindrical form and includes a plurality of concentric external rings which facilitate cutting the sleeve or coupling off at a desired location even with the top surface of the concrete which is to be poured. The coupling is opened at both the lower end and the upper end.
U.S. Pat. No. 4,773,197 to Sullivan, assigned to the assignee of the present invention, discloses a synthetic resin air duct boot which is used for connecting an air duct laid in or beneath a slab for a building to a grill or air register by which the air from the duct is circulated into a room or enclosed space. The air duct boot of Sullivan includes a housing which is of generally right parallelepiped configuration, and includes substantially horizontally extending bottom and top walls interconnected by side walls. A protuberant rib extends around the housing near the top wall, and defines a location at which a portion of the housing may be easily removed after the air duct boot has been placed in position, and a concrete slab or pad has been poured to a selected level adjacent to the top of the boot housing. The housing has a generally cylindrical neck which projects outwardly therefrom in a horizontal direction. The cylindrical neck is molded integrally with the housing and includes an outer annular flange portion which is adjacent to an annular shoulder near the free outer end of the circular neck. The annular flange portion and the adjacent annular shoulder form a situs for the location of an O-ring sealing element or other suitable sealing gasket. The end of the tubular air duct can be pressed over the cylindrical neck of the air duct boot, and the O-ring or gasket will form a seal with the interior surface of the duct.
The above-described air duct of Sullivan has worked well, but the structure thereof includes relatively large sections of unsupported planar walls. In the pouring of concrete, inward deflection of these walls may result. If the walls are deflected too far inwardly, there is a possibility of rupture. The present invention solves this problem by providing external ribs and an internal support for the walls which is integrally molded with the structure.